"Why would there be such a significant spike in FISA orders during the first six months of 2016?

Due to legal compliance restrictions Microsoft cannot divulge the
actual number of FISA Court Orders, only the range. As you can see there
was at least a doubling of requests (Prior: 0-499 ~vs~ Now:
1,000-1,499) perhaps much more.

However, simultaneous to the increase in the number of FISA orders,
the requests were on fewer accounts. So FISA using agencies were seeking
more total data but on a smaller number of accounts."